1. Field of the Invention
The present invention relates in general to an ink-jet printer which performs printing by ejecting ink from nozzles toward a recording medium upon driving of actuators.
2. Discussion of Related Art
Recently, in this type of ink-jet printer, the nozzles tend to be disposed at high density for attaining a high degree of printing quality. To deal with this, there is proposed a technique to drive the actuators by a plurality of driver ICs, as disclosed in U.S. Pat. No. 5,896,146 corresponding to JP-A-8-258292.
In the plurality of driver ICs, however, there exists variation in the property thereof generated during production thereof so that a fall time and a rise time of a drive signal outputted therefrom are not constant among the mutually different driver ICs. Accordingly, there is generated a difference in an ink-droplet-ejection property among the nozzles of IC output channel areas which respectively correspond to the mutually different driver ICs. Namely, the speed of ejecting the ink droplet, the volume of the ink droplet, and the ink-ejection stability are adversely influenced, whereby the printing quality of the ink-jet printer is undesirably deteriorated.
FIG. 14A is a view for explaining an ink-jet head in which two driver ICs 300, 301 are provided. FIG. 14B is a view for explaining drive signals which are outputted from the respective two driver ICs 300, 301. This ink-jet head performs color printing operation by ejecting inks of four different colors, i.e., black, yellow, cyan, and magenta. For each of the four different colors of inks, a plurality of nozzle rows are provided. The plurality of nozzle rows are divided into two areas, as seen in a direction of extension of the nozzle rows, that is, an IC1 output channel area corresponding to the driver IC 300 and an IC2 output channel area corresponding to the driver IC 301.
As shown in FIG. 14B, where a rise time Tr1 and a fall time Tf1 of a pulse of the drive signal outputted from the driver IC 300 are respectively shorter than a rise time Tr2 and a fall time Tf2 of a pulse of the drive signal outputted from the driver IC 301, the ink-droplet ejecting speed in the IC1 output channel area corresponding to the driver IC 300 is higher than the ink-droplet ejecting speed in the IC2 output channel area corresponding to the driver IC 301. Where the drive voltage to be applied to the actuators is the same, the volume of the ink droplet to be ejected is determined depending upon the pulse width of the pulse and the timing at which the drive voltage is applied to the actuators. However, there is generated a difference in the volume of the ink droplet between the two channel areas due to the difference in the rise time and the fall time between the pulse of the drive signal outputted from the driver IC 300 and the pulse of the drive signal outputted from the driver IC 301 as described above.
Accordingly, there is caused a difference in the attaching position to which the ink droplet attaches and a difference in the print concentration, between the adjacent two print regions which respectively correspond to the two channel areas corresponding to the respective driver ICs. Where the difference in the print concentration is generated between the two channel areas, a banding phenomenon is caused due to the difference.
It is therefore an object of the present invention to improve printing quality of an ink-jet printer having a plurality of nozzles which are divided into a plurality of nozzle groups and a plurality of drive circuits which are respectively provided for the plurality of nozzle groups.